The invention relates to a sewing machine equipped with an upper thread dyeing mechanism, which is able to carry out a stitching operation while selectively dyeing an upper thread with a desired color.
So far, it has been necessary to prepare so many threads of different colors as required to be used for stitching operation, especially for making pattern stitches and embroidery stitches with a sewing machine, and to selectively use these threads of different colors in dependence upon the kind of stitches. If a sewing machine operator desires to enjoy a complicated embroidery stitches requiring many different colors according to such a conventional manner, the operator is obliged to interrupt the stitching operation so as to change the sewing thread each time a different color thread is required. Such a thread changing operation comprises the steps of stopping the sewing machine, raising a material presser foot of the sewing machine, cutting off an upper thread previously used, removing the upper thread, and then providing the sewing machine with a fresh upper thread of a different color which is to be passed through a number of thread guides, a tensioning device, a thread take-up lever and a needle hole, which is considerably troublesome and time-consuming.
To eliminate such defects and disadvantages, it has been proposed that a sewing machine is provided with a dyeing mechanism by which a white or colorless upper thread is selectively dyed with any given color, while driving the sewing machine. In this case, however, there will be a time lag between when the upper thread is colored by the dyeing mechanism and when a reciprocating needle accompanied by the colored upper thread penetrates a material sewn. Accordingly, when the stitch pattern requires a change in color of the upper thread, a portion of the thread existing between the dyeing mechanism and the needle has been already colored with a previously required color and can not be used for sequential stitching operation.